Process of manufacturing steel



UNITED STATES PATENT GFFICE.

ALFRED EPHER HUNT, OF PITTSBURG, PENNSYLVANIA.

PROCESS OF MANUFACTURING STEEL.

SPECIFICATION forming part of Letters Patent No. 493,090, dated March 7,1893.

Application filed February 1, 1892. Serial No. 419,879. (No specimens.)

To aZZ whom it may concern.-

Be it known that I, ALFRED EPHER HUNT, of Pittsburg, in the county ofAllegheny and State of Pennsylvania, have invented a new and usefulImprovement in the Process of Manufacturing Steel, of which thefollowing is a full, clear, and exact description.

My invention pertains to the manufacture of steel by the open-hearth,Bessemer, or similar processes, and is intended to afford means by whichthe steel can be carburized with accuracy to the required degree, andthe grade and quality of the steel thus determined. Prior to myinvention such recarburization has been done principally by addition tothe V molten steel of iron alloys containing an exable, because thealloys employed are often expensive, and because, in order to introducethe required amount of carbon, by means of an alloy of manganese, forinstance, it is frequently necessary to introduce with it so muchmetallic manganese as to impair the Value of the steel, while ifhigh-carbon pig be used to carburize the steel, other impurities, suchas sulphur, silicon and phosphorus, are apt to pass with it into themolten bath, and to exercise on the product their usual deleteriouseffects. These objections I avoid by the vuse of a carburizing agent ofsolid free carbon, which in the form of charcoal, coke, graphite,anthracite coal, 850., may be obtained cheaply and in a state ofsufficient purity. I have discovered that if manganese alloy be added tothe bath to free the metal from red shortness, and at about the sametime, (and at or near the termination of the refining process) such freecarbon be added to the bath and thoroughly intermingled with the same indefinite proportions, the percentage of combined carbon in the steel canbe raised to any degree desired for commercial results, it can be donewith certainty, and a finer, purer, and in many ways better product canbe obtained than is possible with prior methods of carburization. To thesuccessful practice of this process, four factors are essentiallynecessary; first, that the carbon addition should be made at or near theend of the refining operation, either soon before the metal is tappedfrom the furnace or converter, or after it has been withdrawn therefrominto a ladle, mold or other receiving vessel; second, that the additionof carbon must be accompanied by the addition of .an alloy of manganese,or similarly deoxidizing metallic element, which can ,mercial value;and, fourth, that the carbon must be added so as to be intermingledthoroughly with the molten bath, either by agitation, stirring, or inany other manner. If any of the conditions above noted is absent in theconduct of the process, certain results cannot be attained and certaintyof product is well recognized as indispensable to the commer cial andeconomic success of any metallurgical operation.

My invention therefore, generally stated, consists in an improvement inthe manufacture of steel, in which the metal is first refined in afurnace or converter, so as to bring it to a steely condition, and isthen treated with manganese, or its equivalent, and recarburized bythe-addition and thorough admixture with it of a definite proportion offree carbon (by which I mean solid carbon uncombined chemically withmetals) sufficient in amount to raise the carbon content of the steel toa predetermined point.

My invention is of value both in connection with the manufacture ofsteel in an openhearth furnace and its manufacture in a Bessemerconverter, and the steps of the method as suggested above, may bepracticed either before or after the tapping of the metal. I

have found it however to be of special value Q Q tion is not limited inits scope to the manner of operation herein specified particularly, but

that, as stated in the first claim, it is intended to cover broadly thetreatment of steel after it has been refined by treating with manganeseor its equivalent, and recarburizing by the addition and thoroughadmixture of a definite proportion of free carbon, however and at whatever period after the refining operation, the same beintrodueedandmixed.

The preliminary operation of the openhearth furnace may be conducted inthe usual manner, t'. 8., a bath of pig iron introduced and, melted onthe hearth may be reduced by means of iron ore; or the bath may bediluted with wrought iron or steel scrap until the excess of silicon andcarbon in the pig iron has been oxidized from it; the well-known basicprocess being employed when it is desired to make use of its propertiesof dephosphorization.

WVhen the refining operation has been carried on in the usual way andthe metal is brought into proper condition for recarburization,Iintroduce the carbon in definite proportion, and rabble it thoroughlyinto the bath. This I prefer to do by binding together bundles ofcharred wood with wrought iron bands, attaching them to rabbles andstirring the bath vigorously therewith; or, if desired, powderedcharcoal, coke, anthracite coal, or carbon in other form may beintroduced and stirred into the bath. In any case, however, the carbonmust be introduced in definite proportionsufficienttoraisethepercentageofcombined carbon in the steel to the point desired.

To determine the proper quantity of carbon to be added in this manner,one must know approximately the weight of the bath under treatment, andthe proportion of carbon which acts efficiently in carburization. Thus,in treating a bath of say twenty thousand pounds of molten steel, havingwhen refined after the manganese addition and immediately before thetime of making the carbon addition, acontent of three-tenths of one percent., of carbon, which is desired to be raised to fivetenths of one percent.,it will be necessary to add an amount of carbon equal totwo-tenths of one per cent, of the total weight of the bath, plus theweight of carbon that will be lost in combustion or otherwise withoutdoing useful work in carburizing the steel. This coefficient of loss canbe made to be practically constant in any given mode of introducing thesolid carbon into the steel. Thus in rabbling into the bath (after themanganese addition and before tapping) sticks of solid wood-charcoal (ofhard wood, such as birch, hickory or oak) in the manner above described,the loss amounts to about twenty-five per cent, of the weight of thecarbon, but where powdered anthracite coal and powdered coke are rabbledinto the bath, the loss is much greater, amounting to about fifty percent. Therefore, in the example stated above, using stick charcoal asthe carbnrizing agent, twotenths of one per cent, of twenty thousandpounds equals forty pounds, and to this adding twenty-five per cent, forloss, it follows that fifty pounds of carbon should be added to raisethe carbon content of the steel from three-tenths of one per cent. tofive-tenths of one per cent.

I claim- 1. In the manufacture of steel, the method which consists inrefining the metal, then at or near the end of the refining operationadding to it a deoxidizing agent, and recarburizing the refined metalunder treatment by the addition and thorough admixture of a definiteproportion of solid free carbon proper to raise the carbon content ofthe steel to a predetermined point; substantially as and for thepurposes described.

2. In the manufacture of steel,the method which consists in refining themetal, adding to it a deoxidizing agent, and recarburizing the refinedmetal under treatment by the addition and rabbling into it of a definiteproportion of solid free carbon proper to raise the carbon content ofthe steel to a predetermined point; substantially as and for thepurposes described.

3. In the manufacture of steel, the method which consists in refiningthe metal, adding to it a deoxidizing agent, and rec-arburizing therefined metal under treatment by the addition and rabbling into it whilestill on the hearth or converter a definite proportion of solid freecarbon proper to raise the carbon content of the steel to apredetermined point; substantially as and for the purposes described.

4. In the manufacture of steel, the method which consists in refiningthe metal, adding to it a deoxidizing agent, and recarburizing therefined metal under treatment by the addition and rabbling into itcarbon in the form of sticks in definite proportion; substantially asand for the purposes described.

In testimony whereof I have hereunto set my hand this 30th day ofJanuary, A. D. 1892.

ALFRED EPIIER HUNT.

Witnesses:

R. H. \VHITTLESEY, THOMAS W. BAKEWELL.

